Apparatus for sorting articles normally comprises a deflecting device to cause a moving article to follow one of two paths, the deflecting device being appropriately positioned during the intervals between the arrival of the articles. The deflector may be operated by a solenoid.
Sorting apparatus according to the present invention comprises a deflector movable between first and second positions and located in a path of movement of the articles to be sorted, the position of the deflector ensuring that each article will follow one of two paths; and means for positioning the deflector, the positioning means being characterised by: a stepping motor; a circuit for energising the stepping motor for angular movement in a first direction or in a second opposite direction; means limiting the angular movement of the stepping motor shaft to a first angular position in one direction and a second angular position in the other direction, the angular interval between the first and second angular positions being less than and lying within the angular interval defined by a shaft position of stable equilibrium in the first direction of energisation of the stepping motor windings and an adjacent shaft position of stable equilibrium in the second direction of energisation of the stepping motor windings; and the shaft of the stepping motor being coupled to the deflector such that the deflector is in its first and second positions when the stepping motor shaft is in its first and second angular positions, respectively.
In the preferred form of driving circuit for the stepping motor used in the apparatus according to the invention, the motor has two windings whch are connected in parallel between two transistor circuits, each of which comprises two series-connected transistors of opposite conductivity types with their gates connected together. A control circuit receives a binary signal representing the required direction of rotation and provides two output signals of opposite logic levels. The gates of the two transistor circuits receive the signals of opposite logic levels so that for one state of the gate signals current flows through the two windings in a first direction and for the other state of the gate signals (in which the logic levels are reversed) current flows through the two windings in the opposite direction.